Tray

ABSTRACT

A tray having excellent impact resistance and excellent vibration resistance and capable of stably holding a fixed number of stored objects. A tray ( 1 ) for storing objects having a substantially plate shape is configured such that angle threads ( 10 ) and bottom surfaces ( 20 ) are alternately arranged, the angle threads ( 10 ) include mount surfaces ( 12 ) that are inclined at a given angle with respect to the bottom surfaces ( 20 ) and on which the stored objects are mounted, and the bottom surfaces  20  include convex portions ( 22 ) arranged asymmetrically with respect to a perpendicular line bisecting the length of the angle threads.

TECHNICAL FIELD

The present invention relates to a tray, and more specifically relates to a tray for protectively carrying and storing an object having a substantially plate shape such as a circuit board on which electronic components are provided.

BACKGROUND ART

There are proposed various trays for carrying to a subsequent process a circuit board having a substantially plate shape on which electronic components are provided and storing the circuit board for a given period of time (see Patent Literatures 1 and 2, for example).

CITATION LIST Patent Literature

Patent Literature 1: JP 2000-206194 A

Patent Literature 2: JP 2004-315089 A

A description of a conventional example of the tray for carrying and storing the circuit board will be provided referring to FIG. 6. A tray 100 shown in FIG. 6 is configured such that circuit boards 110 that define stored objects are arranged side by side on a plane in a storage concave portion 102 that is surrounded by side walls 104 and has a given size. The tray 100 is configured such that an antistatic and impact absorbing sheet 112 (preferably, an expanded sheet) is laid on the circuit boards 110 arranged in the storage concave portion 102, and another tray 100 can be stacked thereon (i.e., a so-called stackable tray).

SUMMARY OF INVENTION Solution to Problem

However, the tray having the configuration described above has the following problems.

First, no partitions between the circuit boards 110 are provided to the storage concave portion 102, and accordingly, the circuit boards 110 easily move during carriage. Thus, there are many occasions of breakage and failure of the circuit boards 110 due to impact and vibration during carriage.

Second, if variously sized circuit boards are stored in the tray 100, the number of circuit boards stored in one tray 100 could change according to the sizes of the circuit boards. Thus, inconvenience occurs when checking stock quantity and carriage quantity of the circuit boards stored in the tray.

Third, the antistatic and impact absorbing sheet 112 that is laid between the circuit boards 110 and the other tray 110 causes an increase in volume, which increases carriage cost and storage cost of the circuit boards. In addition, the number of such sheets that become wastes could be large.

An object of the present invention is to overcome the problems described above and to provide a tray having excellent impact resistance and excellent vibration resistance and capable of stably holding a fixed number of stored objects. Another object of the present invention is to provide a tray by which the whole size of trays when stacked can be reduced.

Solution to Problem

Preferred embodiments of the present invention provide a tray for storing objects having a substantially plate shape that includes angle threads, bottom surfaces, the angle threads and the bottom surfaces being alternately arranged, and mount surfaces on which the stored objects are mounted, the mount surfaces being provided to the angle threads and inclined at a given angle with respect to the bottom surfaces.

It is preferable that the bottom surfaces include convex portions defined by projecting portions of the bottom surfaces.

It is preferable that the convex portions are arranged asymmetrically with respect to a perpendicular line bisecting the length of the angle threads.

It is preferable that the convex portions have a height such that when another tray is stacked on the tray so as to be oriented in a direction 180 degrees opposite to the tray, a distance between an opposite surface to a mount surface of the other tray and the mount surface of the tray is substantially equal to a thickness of the stored objects.

It is preferable that the tray further includes side walls that surround the angle threads and the bottom surfaces.

It is preferable that the side walls include leveled portions defined by recessed portions of the side walls.

It is preferable that the leveled portions are disposed asymmetrically with respect to at least one of a perpendicular line bisecting the length of the tray and a perpendicular line bisecting the width of the tray.

It is preferable that the leveled portions have a height such that when the other tray is stacked on the tray so as to be oriented in the direction 180 degrees opposite to the tray, the distance between the opposite surface to the mount surface of the other tray and the mount surface of the tray is substantially equal to the thickness of the stored objects.

It is preferable that the tray further includes orientation discriminating portions arranged asymmetrically with respect to at least one of the perpendicular line bisecting the length of the tray and the perpendicular line bisecting the width of the tray.

It is preferable that the tray further includes a strengthening rib at an outer periphery of the side walls.

It is preferable that the tray having the configuration above is made from a foamed resin, especially from foamed polyethylene terephthalate.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the preferred embodiments of the present invention in which the mount surfaces on which the stored objects having the substantially plate shape are mounted are inclined at the given angle, the stored objects are stably held. In addition, if the number of mount surfaces (angle threads) is fixed, the number of objects to be stored in one tray can be fixed.

Owing to the configuration that the convex portions defined by the projecting portions of the bottom surfaces between the angle threads are arranged asymmetrically with respect to the perpendicular line bisecting the length of the angle threads, when the other tray is stacked on the tray so as to be oriented in the direction 180 degrees opposite to the tray, loads of the stacked tray and the objects stored therein are received by the convex portions. Accordingly, it is not necessary to interpose a cushion sheet between the stored objects and the stacked tray, which can reduce the whole size of the trays when stacked.

By setting the height of the convex portions such that the distance between the opposite surface to the mount surface of the other tray and the mount surface of the tray is substantially equal to the thickness of the stored objects mounted on the mount surface of the tray, when the other tray is stacked on the tray so as to be oriented in the direction 180 degrees opposite to the tray, the stored objects are caught between the upper and lower trays, which prevents breakage and failure of the stored objects due to vibration.

Owing to the side walls that surround the angle threads and the bottom surfaces and include the leveled portions defined by the recessed portions of the side walls and arranged asymmetrical with respect to the perpendicular line bisecting at least one of the length and the width of the tray, loads of the stacked tray and the objects stored therein are received by the leveled portions as in the case of the convex portions. In addition, the whole size of the trays when stacked can be reduced.

As in the case of the convex portions, by setting the height of the leveled portions such that the distance between the opposite surface to the mount surface of the other tray and the mount surface of the tray is substantially equal to the thickness of the stored objects mounted on the mount surface of the tray, when the other tray is stacked on the tray so as to be oriented in the direction 180 degrees opposite to the tray, the stored objects are caught between the upper and lower trays, which provides excellent vibration resistance.

Owing to the orientation discriminating portions that are arranged asymmetrically with respect to at least one of the perpendicular line bisecting the length of the tray and the perpendicular line bisecting the width of the tray, the orientation of the tray can be easily discriminated by referring to the orientation discriminating portions, which improves workability of stacking the trays.

Owing to the strengthening rib at the outer periphery of the side walls, mechanical strength of the tray is improved. By making the tray from a foamed resin, especially from foamed polyethylene terephthalate, vibration resistance of the tray can be further improved.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an external view of a tray according to a preferred embodiment of the present invention.

FIG. 2 is a cross sectional view of the tray shown in FIG. 1 (A-A section in FIG. 1).

FIG. 3 is a plan view of the tray shown in FIG. 1 (viewed from the direction of the arrow B in FIG. 2).

FIG. 4A is an external view of a circuit board that defines a stored object, and FIGS. 4B to 4D are schematic views (cross sectional views) for explaining processes of storing the circuit boards in the trays shown in FIG. 1.

FIG. 5 is a schematic view for explaining a test subject that is prepared as an example according to the present invention.

FIG. 6 is an external view of a conventional tray.

DESCRIPTION OF EMBODIMENTS

A detailed description of a preferred embodiment of the present invention will now be provided with reference to the accompanying drawings. FIG. 1 is an external view of a tray 1 according to the preferred embodiment of the present invention. FIG. 2 is a cross sectional view of the tray 1 (A-A section in FIG. 1). FIG. 3 is a plan view of the tray 1 (viewed from the direction of the arrow B in FIG. 2). The vertical (height) direction mentioned in the following descriptions corresponds to the up and down direction in FIG. 2.

As shown in FIG. 1, the tray 1 according to the preferred embodiment of the present invention is a tray for storing circuit boards 90 having a substantially plate shape on which electronic components are provided, and includes a storage portion 30 in which angle threads 10 and bottom surfaces 20 are provided, and side walls 40 that surround the storage portion 30. According to the preferred embodiment of the present invention, the tray 1 has a monolithic construction of foamed polyethylene terephthalate having excellent heat resistance and excellent cushioning properties.

In the storage portion 30, the angle threads 10 and the bottom surfaces 20 are alternately arranged substantially parallel to each other. Each angle thread 10 has a cross section that is tapered from the bottom surfaces 20 toward the crest. Surfaces of the angle threads 10 that are inclined at a given angle with respect to the bottom surfaces 20 define mount surfaces 12. The circuit boards 90 that define stored objects are to be mounted on the mount surfaces 12 (details are provided later). As shown in FIG. 2, each mount surface 12 has a cross section that is symmetrical with respect to a line passing through a tip portion 14 of the angle thread 10 and bisecting the angle thread 10 (the line C).

The bottom surfaces 20 provided between the angle threads 10 define a bottom surface of the tray 1. As shown in FIG. 1, the bottom surfaces 20 include convex portions 22 defined by projecting portions of the bottom surfaces 20 having a given height, and the convex portions 22 are arranged substantially parallel to the angle threads 10. The convex portions 22 are arranged asymmetrically with respect to a perpendicular line bisecting the length of the angle threads 10 (the tray 1) (the line D in FIG. 3). It should be noted that the configuration of the convex portions 22 shown in the drawings is given as an example. In the preferred embodiment of the present invention, three convex portions 22 are provided to one bottom surface 20. However, it is essential only that the convex portions 22 be arranged asymmetrically with respect to the line D, and the number of convex portions 22 may be increased.

The side walls 40 surround the storage portion 30 in which the angle threads 10 and the bottom surfaces 20 are alternately arranged. As shown in FIG. 2, the height of the side walls 40 is greater than the height of the angle threads 10. Leveled portions 42 are provided to the storage portion 30 side of the side walls 40. The leveled portions 42 are arranged asymmetrically with respect to the perpendicular line bisecting the length of the tray 1 (the angle threads 10) (the line D in FIG. 3) and a perpendicular line bisecting the width of the tray 1 (the line E in FIG. 3). It should be noted that the configuration of the leveled portions 42 shown in the drawings is given as an example. It is essential only that the leveled portions 42 be arranged asymmetrically with respect to at least one of the line D and the line E.

A strengthening rib 44 is provided to the outer periphery of the side walls 40 (the edge of the tray 1). The strengthening rib 44 projects in the horizontal direction from the outer periphery of the side walls 40 and is arranged to enhance mechanical strength of the whole tray 1 against bending stress.

Orientation discriminating portions 46 are provided at two corners among four corners of the tray 1. The orientation discriminating portions 46 are arranged asymmetrically with respect to the perpendicular line bisecting the width of the tray 1 (the line E in FIG. 3). As described above, the tray 1 is configured such that the convex portions 22 and the leveled portions 42 are arranged asymmetrically, and has orientation. Thus, the orientation discriminating portions 46 are provided in the preferred embodiment of the present invention in order that the orientation of the tray 1 can be easily discriminated visually by referring to the positions of the orientation discriminating portions 46. It should be noted that the configuration of the orientation discriminating portions 46 in the drawings is given as an example, and it is essential only that the orientation of the tray 1 can be discriminated visually. The orientation discriminating portions 46 may be arranged asymmetrically with respect to the perpendicular line E bisecting the width of the tray 1 as in the case of the preferred embodiment of the present invention or may be arranged asymmetrically with respect to the perpendicular line D bisecting the length of the tray (the angle threads 10).

A description of the operation of the tray 1 having the configuration described above will be provided referring to FIGS. 4A to 4D. The tray 1 stores the circuit board 90 having the substantially plate shape as shown in FIG. 4A. On one surface of the circuit board 90, various electronic elements such as resistors and capacitors, connectors for providing electrical connection to the outside, and other elements are provided (this surface is referred to as an electronic component-mounted surface 92).

The length of the mount surface 12 (the angle thread 10) of the tray 1 is longer than the length of the circuit board 90 that defines the stored object. As shown in the cross sectional view of FIG. 4B, the circuit boards 90 are stacked such that opposite surfaces to the electronic component-mounted surfaces 92 of the circuit boards 90 are in contact with each other, and are mounted on the mount surfaces 12. To be specific, two circuit boards 90 are mounted on one mount surface 12 (i.e., four circuit boards 90 are mounted on one angle thread 10). By mounting the circuit boards 90 on the mount surfaces 12 of the tray 1 as described above, storage of the circuit boards 90 in one tray 1 is completed.

Then, another tray 1 is stacked on the tray 1 described above as shown in FIG. 4C. The other tray 1 is stacked on the tray 1 so as to be oriented in the direction 180 degrees opposite to the tray 1. In this occasion, by referring to the orientation discriminating portions 46, the other tray 1 can be stacked so as to be oriented in a proper direction speedily and reliably. In the preferred embodiment of the present invention, if the orientation discriminating portions 46 of the tray 1 are positioned on the upper side when seen from the operator, it is necessary only to position the orientation discriminating portions 46 of the stacked tray 1 on the lower side when seen from the operator. In the stacked tray 1, the circuit boards 90 are stored as described above. Thereafter, other trays 1 are stacked thereon one after another so as to be alternately oriented in the directions 180 degrees opposite to one another while the circuit boards 90 are stored in the stacked trays 1 as shown in FIG. 4D.

As described above, the convex portions 22 of the bottom surfaces 20 of the trays 1 are arranged asymmetrically with respect to the perpendicular line bisecting the length of the angle threads 10 (the tray 1) (the line D in FIG. 3). Therefore, when the vertically adjacent trays 1 are stacked so as to be oriented in the directions 180 degrees opposite to each other, the convex portions 22 of the vertically adjacent trays 1 are not completely superimposed, and at least portions of the convex portions 22 of the lower tray 1 are in contact with the bottom surfaces 20 of the upper tray 1. Thus, loads of the stacked trays 1 and the circuit boards 90 stored therein are received by the convex portions 22.

As described above, according to the tray 1, the stacked trays 1 and the objects stored therein are supported by the convex portions 22 of the tray 1. Therefore, loads that are applied on the circuit boards 90 by weights of the stacked trays 1 and the circuit boards 90 stored therein are reduced. In addition, the stacked trays 1 are prevented from biting into one another. Accordingly, it is not necessary to interpose cushion sheets between the circuit boards 90 and the stacked trays 1, which can reduce the whole size of the trays 1 when stacked.

The circuit boards 90 that define the stored objects are mounted on the mount surfaces 12 that are inclined at the given angle with respect to the bottom surfaces 20, and therefore, the circuit boards 90 are stably held. In addition, the height of the convex portions 22 of the tray 1 is set such that the distance between the opposite surface to the mount surface 12 of the other tray 1 and the mount surface 12 of the tray 1 (the size H in FIG. 4C) is substantially equal to the thickness of the stored objects (the thickness of the stored objects mounted on one mount surface 12, and in the preferred embodiment of the present invention, the total thickness of two circuit boards 90). Owing to this configuration, the circuit boards 90 that define the stored objects are stored so as to be caught between the mount surfaces 12 of the tray 1 in which the circuit boards 90 are stored and the opposite surfaces to the mount surfaces 12 of the other tray 1 that is stacked on the tray 1. In other words, the trays 1 that are stacked one above the other prevent the circuit boards 90 from moving, thereby preventing breakage and failure of the circuit boards 90 due to vibration.

As described above, the leveled portions 42 of the sidewalls 40 are arranged asymmetrically with respect to the perpendicular line bisecting the length of the tray 1 (the angle threads 10) (the line D in FIG. 3) and the perpendicular line bisecting the width of the tray 1 (the line E in FIG. 3). In addition, the height of the leveled portions 42 is substantially equal to the height of the convex portions 22. Therefore, when the trays 1 are stacked one above the other so as to be oriented in the directions 180 degrees opposite to one another, the leveled portions 42 of the vertically adjacent trays 1 are not completely superimposed, and at least portions of the side walls 40 of the lower tray 1 are in contact with the leveled portions 42 of the upper tray 1. Accordingly, loads of the stacked trays 1 and the circuit boards 90 stored therein are received not only by the convex portions 22 but also by the leveled portions 42 (the side walls 40).

As described above, according to the tray 1, the stacked trays 1 and the objects stored therein are supported not only by the convex portions 22 but also by the leveled portions 42 (the side walls 40). Therefore, the advantageous effect of reducing loads on the circuit boards 90 that define the stored objects is enhanced. In addition, the stacked trays 1 are prevented from biting into one another.

The tray 1 has a fixed number of mount surfaces 12 on which the circuit boards 90 that define the stored objects are mounted, and the number of circuit boards 90 mounted on one mount surface 12 is fixed. Therefore, the number of circuit boards 90 stored in one tray 1 is fixed. Thus, it is easy to perform number control (stock number control or carriage number control) of the circuit boards 90 that define the stored objects.

Example

Hereinafter, the present invention will be concretely described with reference to an example.

The tray 1 having the configuration according to the preferred embodiment of the present invention was evaluated in the vibration test and the drop test described below. As shown in FIG. 5, ten trays 1 having the shape given in Table 1 below (made from foamed polyethylene terephthalate) and storing circuit boards having the shape given in Table 2 below (one tray 1 stores 40 circuit boards) were stacked so as to prepare a set 94, two sets 94 were stacked and packed in a resin case 96 of 317 mm tall, 500 mm wide, and 604 mm long so as to prepare a test subject 98.

TABLE 1 Whole size of tray (length, width, height) 543, 446, 245 (mm) Size of storage portion (length, width) 504, 419 (mm) Length of angle thread (bottom surface) 504 (mm) Width of angle thread 26.2 (mm) Height of angle thread 18.2 (mm) Angle of mount surface 35.7 (degree) Width of bottom surface 13.7 (mm) Length of convex portion (three positions) 177, 170, 57 (mm) Width of convex portion 8.8 (mm) Height of convex portion 10.6 (mm)

TABLE 2 Size of circuit board (length, width, thickness) 500, 20, 1.2 (mm) Weight 34 (g)

Vibration Test

The vibration test was carried out on the test subject. The vibration test was performed with the frequency range of 5 to 50 Hz and the sweep time of 3 minutes. The vibration time was 15 minutes in an X direction, 15 minutes in a Y direction, and 60 minutes in a Z direction (see FIG. 5 for the X, Y, and Z directions).

Drop Test

The drop test was carried out on the test subject. The drop test was performed with impact points at one corner, three edges, and five surfaces (nine positions A to I in FIG. 5). The test subject was freely fallen from a height of 25 cm for the corner and the edges and from a height of 32 cm for the surfaces.

Result

After each of the vibration test and the drop test, the circuit boards stored in the tray 1 were checked for the presence or absence of uplift and dropping off of chip components provided on the circuit boards and for abnormal appearance such as breakage, failure, and deformation, and were measured for the amount of electrostatic charge.

In both of the vibration test and the drop test, there were no uplift and dropping off of chip components provided on the circuit boards and no abnormal appearance such as breakage, failure, and deformation of the circuit boards. The amounts of electrostatic charge of the circuit boards were within a range that does not give functional damage to the circuit boards. The results of both of the tests were favorable. The results show that the tray 1 according to the present invention has excellent shock-absorbing characteristics and excellent antistatic performance.

While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention.

Although the circuit board on which the electronic components are provided is given as an example of the stored object in the preferred embodiment of the present invention, the technical idea of the present invention is applicable to any stored object having a substantially plate shape similar to the circuit board.

Although the tray 1 is made from foamed polyethylene terephthalate in the preferred embodiment of the present invention, the tray 1 may be made from another foamed resin such as foams of polystyrene, polyethylene, polypropylene, and urethane. 

1. A tray for storing objects having a substantially plate shape, the tray comprising: angle threads; bottom surfaces, the angle threads and the bottom surfaces being alternately arranged; and mount surfaces on which the stored objects are mounted, the mount surfaces being provided to the angle threads and inclined at a given angle with respect to the bottom surfaces.
 2. The tray according to claim 1, wherein the bottom surfaces comprise convex portions defined by projecting portions of the bottom surfaces.
 3. The tray according to claim 2, wherein the convex portions are arranged asymmetrically with respect to a perpendicular line bisecting a length of the angle threads.
 4. The tray according to claim 3, wherein the convex portions have a height such that when another tray is stacked on the tray so as to be oriented in a direction 180 degrees opposite to the tray, a distance between an opposite surface to a mount surface of the other tray and the mount surface of the tray is substantially equal to a thickness of the stored object.
 5. The tray according to claim 1, further comprising side walls that surround the angle threads and the bottom surfaces.
 6. The tray according to claim 5, wherein the side walls comprise leveled portions defined by recessed portions of the side walls.
 7. The tray according to claim 6, wherein the leveled portions are arranged asymmetrically with respect to at least one of a perpendicular line bisecting a length of the tray and a perpendicular line bisecting a width of the tray.
 8. The tray according to claim 7, wherein the leveled portions have a height such that when the other tray is stacked on the tray so as to be oriented in the direction 180 degrees opposite to the tray, a distance between the opposite surface to the mount surface of the other tray and the mount surface of the tray is substantially equal to the thickness of the stored objects.
 9. The tray according to claim 1, further comprising orientation discriminating portions that are arranged asymmetrically with respect to at least one of the perpendicular line bisecting the length of the tray and the perpendicular line bisecting the width of the tray.
 10. The tray according to claim 5, further comprising a strengthening rib at an outer periphery of the side walls.
 11. The tray according to claim 1, wherein the tray is made from a foamed resin.
 12. The tray according to claim 11, wherein the foamed resin comprises foamed polyethylene terephthalate. 